1. Field of the Invention
This invention relates to a film formed of an ethylenexc2x7xcex1-olefin random copolymer and used for lapping raw rubber (to be referred to as xe2x80x9ca raw rubber lapping filmxe2x80x9d, hereinafter) and to a raw rubber bale lapped with this film.
2. Prior Art
Since ethylenexc2x7xcex1-olefin copolymer rubber typified by ethylenexc2x7propylenexc2x7diene copolymer rubber is superior in strength, heat resistance, weatherability and the like, it is widely used as parts of automobiles and various industrial products. Ethylenexc2x7xcex1-olefin copolymer rubber is generally formed into a bale. When it is shipped as a product, it is lapped with a lapping film to prevent entry of foreign matters and the like. Polyethylene such as high-density polyethylene (HDPE) or low-density polyethylene (LDPE) is used as a lapping film. When raw rubber is to be kneaded by a close-system type kneader, it is generally fed into the kneader without removing a lapping film and kneaded with a filler, oil and the like. At this time, in a case of a compounding in which the viscosity of the raw rubber is low or when a large amount of oil is added, kneading temperature does not go up to a sufficiently high level in most cases. Therefore, the polyethylene lapping film fed together with raw rubber can not fuse completely during kneading and remain in the compound as an undispersed foreign matter, thereby causing a trouble at the raw rubber processing step.
Therefore, as for compounding in which kneading temperature does not go up sufficiently, the lapping film is stripped before ethylenexc2x7xcex1-olefin copolymer rubber is fed into a kneader in most cases. However, in a case of a bale of ethylenexc2x7xcex1-olefin copolymer rubber having low viscosity in particular, a lapping film if firmly adhered to the bale and hence, it takes time to strip the lapping film from the raw rubber, thereby deteriorating workability.
Because of the above reason, studies have been made on improvement of various types of lapping films. When a low-melting resin is used as a lapping film, it can not be formed into a film or even when it is formed into a film, the resulting film has a low strength and cannot be used as a lapping film. Further, when a raw rubber bale is lapped with a low-melting film and stored for a prolong time, there occurs such a problem that lapping films adhere to one another by fusion and consequently, a plurality of bales cannot be separated from one another.
It is therefore an object of the present invention to provide a novel raw rubber lapping film.
It is another object of the present invention to provide a raw rubber lapping film which has a low melting point and is superior in strength and release properties.
It is still another object of the present invention to provide a raw rubber lapping film which is well dispersed in ethylenexc2x7xcex1-olefin copolymer rubber even when an ethylenexc2x7xcex1-olefin copolymer rubber bale lapped with a raw rubber lapping film is kneaded without stripping the film from the bale, and is free from a trouble in the subsequent rubber processing step.
It is a further object of the present invention to provide a raw rubber bale lapped with the raw rubber lapping film of the present invention, that is, a lapped raw rubber bale of which a raw rubber lapping film can be easily separated from the raw rubber and which can be easily separated from one another.
Other objects and advantages of the present invention will become apparent from the following description.
According to the present invention, the above objects and advantages of the present invention can be accomplished by a raw rubber lapping film formed of an ethylenexc2x7xcex1-olefin copolymer comprising an ethylene unit and an xcex1-olefin unit having 4 to 20 carbon atoms and by a raw rubber bale lapped with this raw rubber lapping film.